Finger jointing machines are used to mill joints in the ends of random lengths of lumber, hereafter referred to as “blocks”. Glue is applied to the joints and the blocks are pressed together to form longer pieces of lumber. This is an oversimplification of a precise, complicated process known as finger jointing, but the focus of this invention is the accurate feeding of finger joint machines with blocks, not the process of finger jointing blocks.
This invention relates generally to an apparatus that requires no human operator and that accepts a controlled delivery of blocks from a linear block feeding means, ensures that every block has an acceptable moisture content and delivers a consistent, correctly aligned and correctly orientated supply of blocks at precise intervals to the finger joint machine's lug or slat chain at a lineal speed that is determined by that finger joint machine.
This invention applies to finger joint machines which use either a chain with lugs spaced at regular intervals thereon or a plurality of chains connected by slats at regular intervals to push a block through the said machine's shaper head or heads. The former type of finger joint machine is referred to as a lug chain finger joint machine and the latter is known as a slat chain finger joint machine. The phrase “lug chain” includes the “finger joint lug chain” and the “finger joint slat chain”, but the phrase “finger joint slat chain” may be used herein when necessary. Lugs or slats attached to the lug chain are referred to as “lugs” herein, ignoring the difference between a lug and a slat. For clarity, the longitudinal left hand end of any apparatus is defined herein as the infeed, where blocks are deposited to be eventually fed to the finger joint machine, unless otherwise illustrated in an accompanying drawing. The right hand end of the same apparatus is defined as the outfeed where blocks are deposited on the finger joint machine. The direction of travel is assumed herein to be from left to right and upstream refers toward the infeed and downstream refers toward the outfeed. The words “sprocket” and “chain” may sometimes refer to a multiplicity of sprockets and/or chains, but the singular is generally used.
Historically, finger joint machines were supplied with blocks manually. FIG. 1 illustrates the steps required to place blocks on a lug chain manually. A supply means 1 deposits blocks 2 on an accumulation table 4, where a person 3 picks up a block 2, aligns and places it on the finger joint machine's 6 lug chain 7. Human dexterity became incapable of placing a block in each lug 5 of the lug chain 7 as lug speed and operating speed increased. Empty lugs represent lost production, increased costs and less profit. Workers also suffer injuries while placing blocks manually on lug, thereby increasing production costs with production down time, employee sick leave, various forms of compensation, new operator training and rehabilitation of the injured worker.
Mechanical lug loaders were invented to supplement or replace manual lug loading and work with varying degrees of success. Some individuals, such as Hill, U.S. Pat. No. 6,189,682, U.S. Pat. No. 5,617,910, Cromeen, U.S. Pat. No. 4,429,784, U.S. Pat. No. 4,246,943, Hahn et al., U.S. Pat. No. 4,039,108, and others, were awarded patents for their inventions. Others put their inventions to work in their own manufacturing operations without patent protection.
Lug loaders have generally comprised four separate means to accomplish the task of placing blocks on lug: a supply means, a powered accumulation means, a control means and a powered transfer means.
FIG. 2 illustrates the steps required to load a finger joint machine's lug chain 7 with blocks 2 using a lug loader (sensors and electronic means required to control the lug loader have not been shown).
A supply means 1, which may be a vibrating conveyor, belt conveyor, or some other means, deposits blocks 2 in a haphazard and random fashion on an accumulation means 9, where a person 3 manually picks up a block 2, orientates it in a side-by-side, parallel manner with other blocks 2 with its widest face down and one of its ends aligned to a fence 8, which represents a datum line that continues to the finger joint machine's own fence. A fence 8 may be understood as an obstruction that runs longitudinally along one side of the accumulation means 9 from its infeed to its outfeed in a more or less straight line. Workers must ensure that blocks 2 always maintain contact with the fence 8 and that blocks 2 remain at right angles to the fence 8, because block ends may not be milled correctly by the finger joint machine 6, if they are placed on the lug chain 7 at some distance from the fence 8.
The block is then moved under the powered brush hold down 12 on the accumulation means 9 and is pushed in the direction of travel until it is stopped at the control means 10. The control means 10 releases blocks 2 onto the transfer means 11 at intervals synchronized with the lugs 5. Synchronization may be achieved by electrical or mechanical means and various means, such as levers or pinch rolls employing pressure cylinder means, are used to release blocks from the accumulation means 9 to the transfer means 11.
The transfer means 11, that bridges the gap between the accumulation means 10 and the lug chain 7 is the focus of this invention. Prior art transfer means have generally been comprised of two features: a form of table that blocks lie on and an overhead conveying means. The table generally has a low coefficient of friction and may be comprised of sheet metal, skate wheels, or synthetic materials such as UHMW, which encourage the overhead conveying means 12 to push the block 2 across the transfer table 11 smoothly. The overhead conveying means 12, which may be comprised of a powered brush hold down or a powered, narrow polyethylene belt conveyor, applies pressure against the block 2 and pushes it across the transfer table 11 and deposits the blocks 2 on the lug chain 7. Overhead conveying means 12 usually require precise adjustment for block thickness to work satisfactorily, otherwise malfunctions may occur.
Problems often occur when block lengths vary significantly, for example 5½″ to 55″, because the longer length blocks tend to push around the shorter blocks on the accumulation table and under the powered hold down. Problems also occur on the transfer table because one end of a block is controlled better than the other. In each case, this causes one end of the block to lag behind the other, which may cause the block to move away from the right angled orientation required by the finger joint machine. Various means, such as powered hold down brushes, have been developed to remedy this problem, with limited success, and manual intervention is usually required to ensure satisfactory block alignment for the control means.
A finger joint machine may tolerate some poor orientation and misalignment, but mismanufacture and/or damage may occur if blocks become seriously disturbed, especially if a block jams between the finger joint machine's lugs.
Another embodiment of a transfer means is illustrated in FIG. 3 and uses a large transfer table 11 with a plurality of chains 14 with lugs 15 attached at regular intervals which usually mimic the lug spacing on the finger joint machine's lug chain 7. The transfer chain 14 is usually driven by the finger joint machine 6 and may be linked directly by sprocket and chain means 16 to the finger joint machine 6 or may use a short transfer plate and an overhead brush feeder, similar to that shown in FIG. 2. In all cases, the transfer chain 14 returns underneath the transfer table 11. Even ending rolls may be located longitudinally between the transfer chains 14 to align one end of each block 2 against a fence 8.
Blocks 2 are aligned in a linear block feeding means 18, which releases blocks 2 to the transfer table 11 at regular intervals timed to the passage of lugs 15 on the chain 14. This presupposes that blocks are singularized and oriented for positioning in the linear block feeding means 18 at a distance from the transfer table 11.
This transfer method controls and maintains blocks 2 in alignment better than the previous methods lug loading methods described above, but each lug 14 and each chain way 17 represent possible obstructions to blocks as they are fed on to the transfer table 11 by the linear feed conveyor 18. Blocks can become misaligned between lugs or ricochet off the lugs or chain ways when they hit an obstruction at high speed. The invention does not present such obstacles to the blocks: it uses a smooth belt, a smooth, flat table and solid slats thereby eliminating obstructions.
Prior art transfer tables and lug loaders do not include a means to determine block moisture content and a means to process those blocks with unacceptable moisture content. However, block moisture content is critical to the glueing and glue curing process of finger joint lumber manufacturing, because incorrect block moisture content may cause glue line failure and the rejection of a manufacturing shift's total production output.
This invention differs from prior art significantly in the use of moisture detectors and an overhead return slat chain. The machine will align blocks accurately, reject blocks with unacceptable moisture content and deposit blocks at precise and controlled intervals on the lug chain, regardless of block length variance, and at any lineal speed that the lug chain may run at. No manual labor or adjustments are required of the invention.